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Title: O'Brien in Niagara County

Description: In 1875 New York census John O'Brien was living in Hartland with sons Patrick & John. John Jr. was married with 2 children. I know by 1880 John Jr & family were in Wisconsin. I can't find John St. He was born abt. 1807 in Ireland and I expect he died in Hartland which is why the others left. (Patrick seems to have become a servant of the local priest). How can I find a death record for John sr.?